I wouldn't use the DT990 250 ohms without an amp let alone the 600 ohms! You greatly run the risk of underdriving them and damaging the drivers! Seriously, do not use them until you have at the very least a high gain CMOY. Especially don't us the EQ as an "amp", you should only attenuate with an EQ.
8/20/12 at 10:57pm